A novel slow extraction system for the U-70 synchrotron of the IHEP (Protvino) is presented. The system has been routinely employed since 2013 to extract carbon-nuclei beams with an intermediate energy (455 MeV/nucleon) for applied fixed-target radiobiological research. Issues of the beam dynamics and engineering implementation of the system are considered. The results of experimental beam observations in the U-70 machine are presented, which prove the adequacy of the design approach.

The first results of Proton Radiographic Facility operation on the beam with energies of 50–70 GeV extracted from the U-70 synchrotron at the Institute for High Energy Physics are presented. This facility is capable of forming proton radiographic images of samples with an optical thickness as large as 450 g/cm2 and a field of view of 220 mm or more.

A radiographic facility, placed in the initial rectilinear part of the injection channel, which is intended for transporting a proton beam from U-70 into an accelerator-storage complex, is described. It is designed for energy 50 GeV with field of view 60 mm and makes it possible to obtain an image of objects with optical thickness to 400 g/cm2 with resolution 100 μm. The first static and dynamic experiments performed in our country at 50 GeV have shown the advantages of pulsed radiography in studying fast processes in ultradense media.

Описана радиографическая установка ускорителя протонов с энергией 70 ГэВ ГНЦ ИФВЭ. Установка создана с использованием имеющейся инфраструктуры в начальной прямолинейной части канала инжекции. Линзы канала инжекции предназначены для транспортировки протонного пучка из У-70 в ускорительно-накопительный комплекс и имеют диаметр 100 мм. Установка рассчитана только на энергию 50 ГэВ с полем обзора 60 мм и позволяет получать при наличии некоторых потерь в канале изображение объектов с оптической толщиной свыше 300 г/см2. Оптическое разрешение установки составляет 0.25 мм. В период 2004–2008 гг. на установке проведен ряд экспериментов с многокадровой регистрацией быстропротекающих процессов. При проведении динамических экспериментов использовались малогабаритные взрывозащитные камеры, а также измерительная система мониторинга состояния камеры и окружающей среды.

A radiographic facility for the 70-GeV proton a ccelerator of the Institute for High Energy Physics is described. The available infrastructure in the initial straight part of the injection channel is used in the facility. The 100-mm-diameter lenses of the injection line ar e intended for transportation of the proton beam from the U-70 accelerator to the accelerating-storage complex. The facility has been designed only for an energy of 50 GeVwith a viewfield of 60 mm and used for imaging of samples with an optical density of > 300 g/cm(2) in the presence of some losses in the line. The optical resolution of the facility is 0.25 mm. A set of experiments aimed at multiframe recording of fast processes were conducted on the facility in 2004-2008. Small-sized explosion-proof chambers, as well as the measuring system for monitoring the state of the chamber and environment, were used in the dynamic experiments.

The momentum dispersion of the proton beam extracted from the vacuum chamber of the U-70 accelerator by channeling was measured for the first time. At an 80-mrad bending angle of the Si single crystal, the following beam parameters were attained: an intensity of 10 7 protons/s for 10 12 protons/s hitting the crystal, momentum dispersion of the beam Δ p / p = 0.13%, and a background particle admixture of 0.03% or less.

A station for splitting a 50-GeV proton beam using a bent crystal is described. Intelligent design of the bending device is a specific feature of this station, which minimizes loss of particles in beam splitting. The commissioning of the new station has made it possible for two experimental setups to operate at a time.

Slow extraction system of the accelerated proton beam from U-70 is used for physical experiments with the counting principles with the spill duration of 1-2 seconds on the flat-top magnetic field at energy 50-70 GeV. The slow extraction system commissioning took place in 1979. Initial efficiency of an extraction did not exceed 8385%. Inclusion in extraction system an electrostatic deflector with the wire septum of 0.1 mm thickness has allowed to simplify the scheme of an extraction which began to contain only two septum-magnets in 24-th and 26-th straight sections. Extraction efficiency was 85-87% that was insufficiently for an extraction of intensity more 1·10 ppp. Modernization of the system of the resonant extraction with inclusion in structure of the accelerator two additional quadrupole lenses has allowed to increase structural − β function in the location of electrostatic septum to reduce losses on it and on the first septummagnet three times and reach extraction efficiency 95±2%. For suppression of modulations of intensity of an extracted beam the method of phase displacement on RFseparatrices of 200 MHz is used. Effective time (duty factor) of an extraction reaches thus 95%.

The purpose of this work was to increase the efficiency of slow extraction of accelerated protons from the U-70 accelerator in order to provide the extracted beam for a physical setup requiring high intensity. On account of the limited power of the first extraction setup – an electrostatic deflector, the angle spread of the beam near the deflector barrier had to be decreased in order to decrease the losses and increase the efficiency. For this, the structure function β was increased by inserting two additional quadrupole lenses into the magnetic structure of the accelerator. As a result of the inadequate strength of the system which corrects the frequencies of the betatron oscillations at the maximum accelerator energy 70 GeV, the beam was extracted at energy 64 GeV, where the frequency of the vertical betatron oscillations could be set above the line of the resonance 4Q z = 39. As a result, the losses at the first two extraction setups increased by a factor of 3 and the efficiency of the slow-ejection system increased from 85% to 95%.

A method for extracting a proton beam from the U-70 IHEP synchrotron using a bent silicon crystal at a simultaneous operation of several internal targets is described. The optimal range of the crystal bending angles is 0.5–2.5 mrad, and the crystal length along the beam is 2–5 mm. The extracted-beam intensity can be varied from 107 to 6.0 × 1011 protons per cycle of the U-70 operation, depending on the requirements of physical experimental installations. The method developed for the accelerated-beam extraction with the use of short crystals significantly extends the possibilities of conducting physical experiments on the accelerator.

Bent crystal was extracting 70-GeV protons with average intensity 4*10^11 (as measured in external beamline) per spill of 1.6 s duration, in parallel to the simultaneous work of two internal targets in the accelerator ring. An additional crystal, placed in the external beamline, was deflecting a small part of the extracted beam with intensity 10^7 protons toward another physics experiment. Crystal-extracted beam had a typical size of 4 mm by 4 mm fwhm at the end of the external beamline. Measurements for the extraction efficiency and other characteristics at the simultaneous work of four experimental set-ups are presented. With crystal working in the above-said regime during one month, no degradation of channeling was observed. The studies of extraction efficiency have been continued with new crystals.

A substantially increased beam extraction efficiency can be achieved in the case of a multiple beam’s passage through a crystal. This suggestion was verified in experiments with short (5–7 mm long) curved single crystal with bending angles of 1.5–1.7 mrad performed at the Institute of High Energy Physics. The peak effiency values obtained were 47±3%, and the maximum average efficiency was 42±2% for a 23% intensity taken from an accelerated beam. The maximum extracted beam intensity was 6×1011 protons per cycle.

Using channeling in a 5-mm crystal with a bending angle of 1.5 mrad, a radical increase in the efficiency of beam extraction from accelerator was achieved due to an increased number of particle encounters with crystal. The measured world-highest efficiency of crystal extraction, over 40%, is in good agreement with theory predictions. The extracted beam intensity of 6 ×10 ppp was obtained, five orders of magnitude higher than previous results.

A record-high particle extraction efficiency, exceeding 40%, in agreement with theoretical predictions, is achieved using a short (5 mm long) crystal bent by 1.5 mrad. An extracted beam intensity of ∼6×10 11 protons per cycle is obtained. This is five to six orders of magnitude higher than previous results.

A radical increase in the efficiency of beam extraction from an accelerator is achieved with a short (7 mm long) crystal bent by a small angle (1.7 mrad) by increasing the number of times particles pass through the crystal. A particle extraction efficiency of ~20%, in agreement with the prediction of the theory, was achieved experimentally. A record high intensity of the extracted beam 1.9×10 11 protons per cycle, which is four orders of magnitude higher than previous results, is obtained.